Deep in the flesh of the Taupō volcanic zone, they’re digging for fire. And there’s a lot riding on it.

You don’t have to read too widely on the potential of superhot geothermal – also known as superdeep and supercritical – to encounter terms like “silver bullet” and “holy grail” in high rotation. 

For climate change, for energy security and for the future of New Zealand’s economy, this could be a gamechanger, say those involved.

That’s a lot of pressure. Is it over the top? “It’s over the top only if you don’t understand that the project may fail,” said Tim Groser, chair of the GeoShot NZ project. “But if the project succeeds, all of the above are true.

Speaking to The Spinoff for an episode of At Large with Toby Manhire, the former trade minister and ambassador to the US said: “This is an extraordinary opportunity for New Zealand to both change the long-term energy structure of our country, and also I think, possibly, it is the biggest single positive thing to change our emissions profile in terms of climate change.”

The wider project, commissioned by the government at a cost of more than $60 million, combines the brain and brawn of Earth Sciences New Zealand, universities, power companies and mana whenua. It centres in practical terms on work under way at Rotokawa, home to an “exploration well” drilled by Todd Energy’s “Big Ben” rig.

There is substantial geothermal energy feeding in the New Zealand network already, but supercritical plugs into a different golden layer, or “brittle-ductile transition zone”. Around 5km under the surface, with heat topping 374C and 220 bars of pressure, water goes into that “supercritical” state. If it works at Rotokawa, it could be replicated across similar sites. Advocates say it would be close to an inexhaustible resource. 

By the estimate of the International Energy Agency, the accessible heat beneath the surface of the Earth could meet humanity’s electricity needs something like 140 times over.

The possibilities the technology offers are encapsulated, said Groser, in research suggesting that “tapping into just 1% – repeat, 1% – of the estimated potential of the United States’ superhot rock potential could generate clean renewable power equivalent to eight times the country’s 2022 electricity consumption.”

There are some hefty practical challenges – not least engineering a drill that can withstand the extreme heat, something that has so far defied efforts in Iceland, another fiery terrain. 

But the political buy-in was gratifying, said Groser. Shane Jones had championed the research, while senior MPs on Labour, he said, were “totally supportive of it. I think we’ve got strong, probably multi-partisan political support.” 

He added: “I spent all of my career really trying to address the structural problem New Zealand had on trade. And I always say, when I was our chief trade negotiator, before I was trade minister, that if I and my teams hadn’t had strong political support from David Lange, [Jim] Bolger, Helen Clark – the whole range of prime ministers – we would never have solved that problem.

“So, getting on a long-term project that is far longer than the political cycle, you don’t need complete unanimity between the centre-left and the centre-right, but you need them to agree on the direction of travel, and they need commitment to that.”

The supercritical opportunity, Groser stresses, is complementary to – rather than an as-well-as, rather than instead of – other renewable sources.

“Geothermal is the most beautiful renewable complement to wind and solar, and if we can succeed in this extraordinary project that I’m involved in, in accessing vast increased amounts of renewable energy from geothermal, this then validates the investments in wind and solar. So the three really go together like a set of beautiful ingredients in a good recipe.”

As for environmental concerns, lessons had been learned from previous geothermal prospecting, said Groser. “We will design the wells to ensure that damage to existing taonga on the surface does not occur, and in principle, there’s no difference between drilling a bit deeper for these wells than drilling the conventional 2-3km wells. The same issues, the same risks arise. Going another kilometre or so isn’t going to change the nature of that.”

It might fail, no doubt about that. But what is Groser’s hunch? What chance of a breakthrough in the next decade or so? “The engineers – I’ve repeatedly asked them that question. They’ll never be pinned down,” he said. 

“It’s like asking a builder how much it’s going to cost to renovate your bathroom. It  feels to me like a 70-percenter. I’ll be both disappointed and slightly surprised if it doesn’t.” The current project is only a beginning, but the hope is to “produce enough data for us to go to whoever is the next government and say: this is really interesting.” he said. “We need to do more, but the prize is really considerable.”